1. Field of the Invention
Aspects of the present invention relate to a non-volatile memory device and a fabrication method of the non-volatile memory device. More specifically, aspects of the present invention relate to a non-volatile memory device formed on a substrate, such as a glass substrate, and a method of fabricating the non-volatile memory device, and a memory apparatus including the non-volatile memory device.
2. Description of the Related Art
Generally, a non-volatile memory device may be classified as a floating-gate memory device and a charge-trapping memory device. The floating-gate memory device is a device for maintaining data by using a potential well. The charge-trapping memory device is a device for maintaining data by trapping charges in a trap region inside a nitride film or a trap region present in an interface between the nitride film and an insulator.
A representative structure of the charge-trapping memory device is a Silicon-Oxide-Nitride-Oxide-Silicon (SONOS) structure. Typically, the SONOS structure may include a sequential stack of a semiconductor substrate, an ONO structure, and a gate electrode. The ONO structure may include a sequential stack of a tunneling oxide film, a nitride film, and a blocking oxide film. The tunneling oxide film may enable electrons to tunnel into a trap region inside the nitride film or a trap region of an interface of the nitride film. The blocking oxide film may block charges from moving between the nitride film and the gate electrode. The trap region may store charges. Source/drain regions may be provided on the semiconductor substrate on either side of the above stack.
A recent trend has been the formation of a non-volatile memory device on a glass substrate. Such a device may include a sequential stack of the glass substrate, the ONO structure, and the gate electrode. The glass substrate may include a protective layer (e.g., a buffer oxide film) thereon to protect the glass substrate. A polysilicon layer may be provided on the protective layer. Source/drain regions may be provided on the polysilicon layer on either side of the above stack.
Forming the polysilicon layer may include crystallizing an amorphous polysilicon layer (e.g., by irradiating the amorphous polysilicon layer with a laser). Thus, surfaces of the polysilicon layer may be rough and non-uniform, which may result in generation of a large leakage current. In other words, a leakage current thereof may be significantly increased due to the roughness and the non-uniformity of the surfaces of the polysilicon layer. Therefore, such a non-volatile memory device may function abnormally during programming/erasing operations.